class_docstr: A stream operator that counts the number of non-missing values.
code: def __init__(self) -> None:
      super().__init__(lambda w: (~np.isnan(w)).sum())
  
imports: from typing import Callable, List
  import numpy
  from tensortrade.feed.core.base import Stream
  from tensortrade.feed.api.float import Float
label_desc: Use image node_id 1 to create a new ExpandingCount object from inherited base classes: ExpandingNode with example: obj = ExpandingCount()